Multiple point injection of hydrogen donor diluent in thermal cracking

Abstract

An improved hydrogen donor diluent cracking process for upgrading hydrogen deficient hydrocarbonaceous materials such as petroleum residua to more valuable liquid distillates. The hydrogen donor diluent, which is a material that has been partially hydrogenated and which readily gives up hydrogen under thermal cracking conditions, is injected into the cracking unit at a plurality of points so that the ratio of the rate of hydrogen transfer to the rate of cracking is more uniform throughout the cracking unit than if all the hydrogen donor diluent is injected with the feed charge to the cracking unit.

What is claimed is: 
     
       1. In a conversion process wherein a heavy petroleum residuum is subjected to hydrogen donor diluent cracking conditions in the presence of a hydrogen donor diluent material in a cracking unit, the improvement comprising: adding a first portion of the hydrogen donor diluent to said petroleum residuum as it is charged to said cracking unit, and adding a second portion of the hydrogen donor diluent to said petroleum residuum at a point in said cracking unit downstream from the petroleum residuum inlet thereto.   
     
     
       2. The process of claim 1 wherein the hydrogen donor diluent is introduced to said cracking unit in a manner whereby the ratio of the rate of cracking of said residuum to the rate of hydrogen transfer from said diluent is approximately constant throughout said cracking unit. 
     
     
       3. The process of claim 1 wherein a first portion of said hydrogen donor diluent is introduced into said cracking unit with the petroleum residuum feed, a second portion of said hydrogen donor diluent is introduced into said cracking unit approximately midway therethrough, and a third portion of said hydrogen donor diluent is introduced at or near the outlet of said cracking unit. 
     
     
       4. The process of claim 3 wherein said first portion and said second portion are approximately equal. 
     
     
       5. The process of claim 4 wherein said first portion of said diluent is from 40 to 60 volume percent of the total volume of donor diluent.